The diester aromatic products of this invention are confined to the scope of the generic formula shown below: ##STR1## wherein R' is an alkyl radical of 1 to 8 carbon atoms and the two acetate ester groups can be meta, ortho or para to each other.
The diester products of this invention are produced by the overall reaction shown below in which the preferred dimethyl para or ortho-phenylenediacetate esters are the preferred product. ##STR2##
The preferred dimethyl p-phenylenediacetate is useful as a monomer for polyester copolymers as well as other polymeric formulations.
The closest prior art for preparing the preferred product, dimethyl p-phenylenediacetate, is believed to be reported by R. F. Heck and D. S. Breslow in J. Amer. Chem. Soc., 85, 2779 (1963), who disclose a 32% yield of p-phenylenediacetic acid using near stoichiometric amounts of a cobalt carbonyl catalyst. Applicants have found that using the same dihaloxylene starting materials but PdCl.sub. 2 (PPh.sub.3).sub.2 as the homogeneous catalyst up to 56% yield of product is formed at initial dihalide to palladium mole ratios of 50 or higher. Quite unexpectedly good yields are obtained under non-forcing, low temperature and pressure conditions using the 2-component catalysts such as PdCl.sub. 2 (PPh.sub.3).sub.2 in the absence of Group IV metal halide co-catalysts such as SnCl.sub. 2 which are needed to achieve carbonylation of vinylic halides*. FNT * Ser. No. 372,899